1. Field of the Invention
This invention relates to inductor devices and more particularly to voltage regulating transformers or ferroresonant transformers.
2. Description of the Prior Art
Ferroresonant transformer circuits also called constant voltage stabilizers, ballasts, constant voltage and/or current regulators, voltage regulating transformers and the like produce a substantially constant voltage, wattage or current output from a variable alternating voltage source. In general, such devices are driven by a sinusoidal electrical signal but square or other wave-shaped driving forces may be used to power the ferroresonant transformer. Many of these devices are used in high-intensity discharge lamp regulators or ballasts since such lamps require a substantially high starting voltage (open circuit voltage) in order to ignite the lamp. Before ignition takes place, the impedance of these lamps is almost infinite. After ignition takes place, the impedance of the lamp approaches zero and the current must be restricted by using an impedance in the external circuit. Each type of the high-intensity discharge lamps for example Mercury, Metal Halide, Sodium, etc. has an operating voltage, current and current crest factor for optimum operation, but all of the high-intensity discharge lamps have a high starting voltage and a very low impedance after ignition. It is therefore necessary to limit the current through the lamp by using the inductive-capacitive reactances of the regulator or the ballast circuit. However, the regulator and ballast circuit must be designed and constructed to meet maximum and minimum voltage requirements of the American Standards Association (ASA) specification C-78.1305-1965 or later revisions.
One undesirable characteristic of a mercury vapor lamp occurs when power is interrupted for one or more cycles after being in full operation. The arc is extinguished and will not reignite until the lamp cools or unless the hot lamp is subjected to a greater voltage than that originally to start the cool lamp. After cooling and reignition, the lamp undergoes a normal warm-up which may take between 10 and 20 minutes depending upon operating conditions. If a large factory is equipped with mercury vapor lamps and a short duration power failure occurs, the factory will be without suitable lighting for a period of 10 to 20 minutes.
Some in the prior art (U.S. Pat. No. 2,858,479 issued Oct. 28, 1958) have established an oscillation in the secondary winding to provide harmonic distortion of the magnetic flux to increase the peak voltage of the transformer. The disadvantage of the harmonic distortion was that the harmonic current continued after ignition of the lamp expending power without flowing through the lamp.
In my prior U.S. Pat. No. 3,688,232, I disclosed a novel apparatus for reducing the amount of material required in a transformer by graded capacitance and graded insulating material for optimum distribution of voltage and current through the transformer. Since this teaching is pertinent to the present invention, I hereby incorporate by reference said patent into the instant disclosure.
Accordingly, it is an object of this invention to overcome the aforementioned disadvantages of the prior art and to provide a voltage regulating transformer having means for modifying the magnetic flux in the magnetic core to increase the magnetic flux during each cycle to produce a higher peak output voltage in the secondary portion of the core.
Another object of this invention is to provide a voltage regulating transformer having a harmonic voltage in the secondary winding for producing a higher peak output voltage and which harmonic voltage is usable to power the load after ignition.
Another object of this invention is to provide a voltage regulating transformer incorporating oscillation in the secondary winding within a sectionalized integrated transformer as disclosed in my prior U.S. Pat. No. 3,688,232.
Another object of this invention is to provide a voltage regulating transformer having not only optimum inductance and capacitance but also current and voltage distribution to reduce cost and weight of the transformer.
Another object of this invention is to provide a voltage regulating transformer having integrated inductive and capacitive reactances thereby reducing the bulk of the transformer.
Another object of this invention is to provide a voltage regulating transformer having means to provide a voltage large enough for igniting a warm mercury vapor lamp after it has been extinguished and still be constructed within the voltage tolerances of the aforesaid ASA specification.
Another object of this invention is to provide a voltage regulating transformer including sectionalized capacitances interconnected by coupling capacitors to obtain a peak starting voltage capable of starting or restarting a cold or warm High Intensity Discharge (HID) vapor lamp.
Another object of this invention is to provide a voltage regulating transformer which can be easily wound on conventional coil and capacitor winding machines.